1. Field of the Invention
The present invention relates to granular material feeders for screw auger conveyers, and more particularly to funnel shaped attachments to the input ends of flexible screw augers that include grater-blade slot openings or scoops outside, and blades or flow-guides inside to boost the picked-up materials to almost the rotational speed of the funnels themselves.
2. Background
Cohesive materials can sometimes be a problem to transport from a drilling site to a collecting and processing site, especially in microgravity environments. Granular solids cannot simply be pushed along inside a cylinder with a piston. So screw conveyers have been conventionally used for transporting free-flowing granular solids over modest distances.
The present inventor, Otis Walton, describes a few centrifuging conveyers for moving granular solid materials over a wide range of cohesion strengths, in U.S. Pat. No. 8,607,966, which issued Dec. 17, 2013. A screw auger is fixed to the outside surface of a fixed inner shaft. A matching, but rotating outer pipe is slipped over the outer diameter of the auger screw. The outer pipe is rotated at a high enough rate to induce granular materials introduced at an input end to cling to the outer pipe's interior walls. The auger screw will act on these clinging layers to move the granular material along to an outlet end, without clumping or clogging.
These centrifuging conveyers need feeders that can introduce granular solid materials at an input end that are boosted in speed enough to have the necessary centrifugal forces come into action. Vertical and steeply inclined orientations need specially adapted scoop-type feeders, as illustrated by FIG. 4B in U.S. Pat. No. 8,607,966. Granular solid material is scooped into conical feeder 409 externally louvered scoops 410. Axially tapered and tilted inner blades 411 ramp up and boost the introduced materials to near the speed of rotation of conical feeder 409 to start the materials moving along toward the outlet end in the layers clinging to the interior walls.
The outer pipe rotates on its axis at a rate high enough for even cohesive materials to form in layers on the interior walls. Curved auger screw blades that are either stationary or rotated at a different rate move the materials along inside. As the incoming materials are fed in, a difference in the rotational rates of the interior walls and the set angles of the several blades will dictate how fast the cohesive material is moved along the walls of the interior.
The present invention improves over conventional screw-auger conveyors with stationary outer pipes. Conventional screw-auger conveyors rotate only an inner helical screw inside of the stationary pipe. Conventional screw augers typically operate in one of two modes; in orientations where the axis is near horizontal they typically operate with slow rotation of the inner screw, and they function by material moving up the rising face of the rotating helical screw and then sliding back down its advancing face—inducing axial displacement. These slow-rotating augers will stop working if the screw-auger axis is tilted up to steep angles, or in a near-vertical orientation. Near-horizontal auger conveying, at these low rotation rates, depends on gravity to help convey dry granular solids.
Conventional screw-augers can, however, be operated in such a manner that they convey material vertically, but in this case higher rotation rates are involved and the flow modes and mechanisms that move the materials along inside up the length are significantly different from those operating in slowly rotated screw conveyors. Gravity is no longer helping and must be overcome instead.
In this vertical conveying mode the fast-rotating screws fling the material out to the outer interior walls where it can be pushed up along the wall by the helical screw auger as it rotates. The friction of the material moving in a spiral upward path along the outer wall also minimizes the amount of material that falls back down any gap that exists between the screw and wall. High rotation rates are needed to create the high centrifugal force required for this mode of near-vertical screw-conveying to function. However high rotational rates create problems at the bottom inlet feeds.
A majority of heavy industrial vertical screw conveyor are sold with attached, but separately powered, horizontal feed augers to force-feed the inlet. Other vertical conveying systems have scoops on separately rotating outer pipes to force materials into the conveying systems. Feeding vertically oriented conventional screw-auger conveyors is difficult, and few satisfactory solutions have been developed other than the separate horizontal feed augers.
Some attempts to get good enough inlet feeds for vertical screw conveyors have a retracted outer casing at the distal end that exposes several of the screw flights. This arrangement can act as a feeder. But screw extensions out beyond the end of the casing can actually fling material out and away from the screw entry. The centrifugal effects in the swirling material are responsible for feed-starving that gets worse if the rotation rates increase, or gravity is reduced.
Vertical conveying tests under lunar gravity conditions aboard NASA's reduced gravity aircraft with lunar simulants proved fast rotating screws would feed-starve and not be very effective.
There is a general need therefore for a device that can quickly feed enough material into vertical screw-auger conveying systems. And in the field of space exploration and in-situ resource utilization, there is a need for devices to extract subsurface materials through small entry holes into the surface of small airless bodies or moons, e.g., to preserve volatiles from Space. A drill-head feeder is needed for connection to flexible conveying systems when excavating materials. And one that can convey the materials to the surface through a small sealed inlet hole, and thus meet the needs of future space exploration missions.